1. Field of the Invention
The invention relates to a non-magnetic one-component toner for use in an electrophotographic system, a non-magnetic one-component contact developing device and an image-forming apparatus.
2. Description of the Related Art
The non-magnetic one-component contact developing system requires no carrier in developer, and consequently makes it possible to simplify the structure of the developing device. This system requires a blade member which controls the toner layer thickness on a toner-supporting member (for example, developing roller), and toner is subjected to a stress between the toner-supporting member and the blade member. Further, since the toner-supporting member is made in contact with an image supporting member (photosensitive member) so that an electrostatic latent image on the image supporting member is developed, the toner is also subjected to a stress between the toner-supporting member and the image supporting member. For this reason, abrasion and toner fusion tend to occur on the blade member and the toner-supporting member. The subsequent problems are deviations in the toner layer thickness and insufficient toner charging, with the result that image irregularities, faded images and fog are caused.
In order to solve the problems of toner fusion to the blade member and toner-supporting member in the non-magnetic one-component developing system, techniques for controlling the particle size distribution of toner, degree of roundness, hardness and the like have been known (see Japanese Patent Application Laid-Open No. Hei11-125931 (claims 1 and 7, on page 2)).
However, the application of the above-mentioned toner has raised a new problem in that there is degradation in the toner transferring efficiency from the surface of the image supporting member to other members such as recording paper. The insufficient transferring efficiency makes it impossible to omit a device for cleaning residual toner on the surface of the image supporting member in an image-forming apparatus, and also makes it incapable of adopting a so-called cleanerless system. Consequently, it is not possible to reduce manufacturing costs of the image-forming apparatus. Furthermore, when the above-mentioned toner is used for a long time in a contact charging system in which a charging member such as a charging brush is made in contact with the image supporting member to charge the surface of the image supporting member, it becomes difficult to carry out the charging process evenly due to residual toner on the surface of the image supporting member, resulting in image irregularities and faded images.